This invention relates to a gas flow measuring apparatus, and particularly to an air flow measuring apparatus for measuring the amount of flow of air which an engine, for example, sucks.
There has been proposed an apparatus which is arranged to have an electric heater and temperature-dependent resistors in a suction duct of an engine and thereby to detect the flow of intake air (gas to be measured).
This conventional apparatus has an advantage that amount of air flow can be measured with a small-sized and simple arrangement. However, this apparatus employs an electric heater and temperature-dependent resistors which are each formed of a ring member of electric insulating material and a resistance wire stretched across this ring member, so that if the temperature of the intake air (temperature of gas to be measured) is changed, an error associated with measurement is caused by the thermal response difference between the insulating ring member and resistance wire due to their different thermal capacities and by heat transmission at the contact points between the insulating ring members and resistance wires, thus preventing the amount of air flow from being measured precisely.